I've played six games already. It's really interesting how the payment mechanics work to redefine the gameplay. What is implemented (or almost) in https://itch.io/jam/paywall-eden-playgama-xsolla/rate/3621320. Unfortunately, you're right, and I haven't found a good game idea to implement it. I think the same as you do "Paywall Eden is a jam about making in-game purchases actually fun, clever, or surprising — without ruining the player experience". But as far as I understand, the themes presented leave a back door for my implementation too. Invest to save time.